Zooming device

ABSTRACT

A zooming device for a camera, which comprises a rocker which operates a plurality of successively operable switches provided on each side of the center of rotation. The rocker can be turned in either direction to operate the first one of the plurality of switches so as to obtain zooming by a corresponding multiple lens group in the corresponding direction and at a predetermined speed. The zooming speed can be changed to a next speed when a second one of the switches is operated by further turning of the rocker.

FIELD OF THE INVENTION

The present invention relates to zooming devices and, more particularly,to a zooming device which incorporates a switch for shifting thedirection and speed of the zoom by means of a multiplying lens group ofa zooming lens.

BACKGROUND OF THE INVENTION

Prior art zooming devices of this type often include a switch commonlytermed a zooming switch, which determines the shortening or lengtheningof the focal distance according to the direction of zooming by means ofa multiplying lens group. Such prior art devices also often include asecond switch called a zooming speed switch for shifting the zoomingspeed.

One disadvantage of this known arrangement, however, when such zoomingdevices are used in a portable television camera or the like, is that aninconvenience is experienced when the camera is supported by both handsof the operator, in which case, his use of his fingers is restricted.More particularly, in a case when operating the zooming switch and thenoperating the zooming speed switch by changing the finger position whileholding the camera, a deviation of the photographing angle ordisturbance of the image is liable to result. Specifically when theobject moves quickly, in which case, quick zooming operations arerequired, it is difficult to achieve camera stability.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to eliminate theseproblems of the prior art.

It is still another object of the present invention to provide a zoomingdevice in which the direction and speed of zooming by means of amultiplying group can be achieved in a single operation.

It is still another object of the present invention to provide a zoomingdevice of such an arrangement, that will employ the use of a single"seesaw" or rocker type switch.

These and other objects of the present invention will be betterunderstood with reference to the following description of typicalembodiments of the present invention as illustrated in the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings in which the same reference numeralsdesignate the same parts in all views:

FIG. 1 is a schematic representation of one embodiment according to thepresent invention;

FIG. 2 is a circuit diagram showing a rocker switch and a motor drivingcircuit according to the present invention; and

FIGS. 3A and 3B are fragmentary side views illustrating the operation ofthe seesaw switch in which FIG. 3A shows the case when the right sidefirst switch is operated and FIG. 3B shows the case when the right sidesecond switch is operated.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now more particularly to the drawings, one of the preferredembodiments of a zooming device according to the present invention maybe seen in FIG. 1 as comprising rocker switch 1, which is operated byand is included in rocker lever 2, which is rockably mounted on a shaft4 which is secured in bracket portions 3a or a base 3. "Seesaw" lever 2is supported on the opposite ends of a substantially U-shaped spring 5which is mounted on the base 3, and includes movable contacts consistingof spring members that are secured to the opposite ends of the lever 2.Spring 5 thus normally biases rocker lever 2 to a neutral position asshown in FIG. 1. A movable contact 6 faces and co-operates with fixedcontacts 8 and 9 which are attached to the base 3 on one side thereof,while a similar movable contact 7 faces and co-operates with fixedcontacts 10 and 11 secured to the base 3 on the other side thereof.Auxiliary fixed contacts at 8' and 10' are further secured to the base 3and are the same effective height or level above base 3, which commonlevel is higher than the level of the fixed contacts 9 and 11,respectively.

Movable contacts 6 and 7 form first switches with the respective fixedcontacts 8 and 10 and also form second switches with the respectivefixed contacts 9 and 10.

Motor driving circuit 12 for driving a motor 13 is connected to movablecontacts 6 and 7 and also to fixed contacts 8, 9, 10 and 11. The motor13 is coupled to a worm 14, which is in turn coupled to a worm gear 15,which is in mesh with a rack gear 18 secured to a multiple lens group 17constituting part of a zoom lens 16. The zoom lens 16 includes front andrear lens groups 19 and 20, which are coaxial on an optical axis L andare disposed on the front and rear sides respectively of the multiplelens group 17.

Referring now more particularly to FIG. 2, the motor driving circuit 12,includes four transistors Q₁, Q₂, Q₃, and Q₄, for driving the motor 13.Transistors Q₁ and Q₄ may be PNP transistors while the transistors Q₂and Q₃ are NPN transistors. Transistors Q₁ and Q₄ have their collectorsgrounded, while transistors Q₁ and Q₃ have their emitters connected toeach other, and the junction is connected to one of the terminals of themotor 13. Transistors Q₁ and Q₃ are connected to each other, whereas Q₃has its collector connected to a voltage source Vc. Transistors Q₂ andQ₄ have their emitters connected to each other, and the junction isjoined to the other terminal of the motor 13. Transistors Q₂ and Q₄ alsohave their collectors joined to each other and transistors Q₂ has itscollector connected to the voltage source Vc. A resistor R₁ is connectedbetween the collector and base of the transistor Q₂, and a resistor R₂is attached between the collector and base of the transistor Q₃.

The movable contacts 6 and 7 of the rocker or "seesaw" of rocker switch1 are grounded. Fixed contact 9 is joined to the base of the transistorQ₄ and fixed contact 8 is attached to the base of the transistor Q₄through a resistor R₃. The fixed contact 11 is in communication with thebase of the transistor Q₁, while fixed contact 10 is joined to the baseof the transistor Q₁ through a resistor R₄.

METHOD OF OPERATION

When the "seesaw" lever 2 is in its center position as shown in FIG. 1,the movable contacts 6 and 7 are in communication with none of the fixedcontacts 8, 9, 10 and 11 and auxiliary fixed contacts 8' and 10'. Whenthe lever 2 is rocked in either direction, zooming to shorten orlengthen the focal distance can be obtained. In a case when it isnecessary to effect low speed zooming in the shortening of focaldistance direction, the seesaw lever 2 is rocked in the clockwisedirection. As a result, the movable contact 7 is brought into contactwith the fixed contact 10 and auxiliary fixed contact 10'. With theclosure of this switch, a voltage of Vc·R₄ /(R₂ +R₄) is applied to thebase of the transistor Q₁ to cause current from the transistor Q₁ totravel through the motor 13 to the transistor Q₂. At this time, theterminal voltage developed across the motor 13 is substantially Vc·R₄/(R₂ +R₄). When subsequently, it becomes necessary to effect high speedzooming in the shortening of focal distance direction, the seesaw lever2 is further moved clockwise. As a result, the movable contact 7 is bent(see FIG. 3B) until a portion is in contact with the fixed contact 11.With the closure of this switch, the base potential on the transistor Q₁is reduced to ground or zero, while terminal voltage across the motor 13is increased to be substantially equal to Vc.

For zooming operations in the lengthening focal distance directions, theseesaw lever 2 is turned in the counterclockwise direction. As a result,the movable contact 6 is brought into communication with the fixedcontact 8 and auxiliary fixed contact 8'. With the closure of thisswitch, current is caused to flow from the transistor Q₃ through themotor 13 to the transistor Q₄. The voltage developed across the motor13, in this case, is substantially Vc·R₁ (R₁ +R₃) in absolute value andopposite in sense to that in the previous case when the seesaw lever 2was turned in the clockwise direction, i.e., the positive supply and theground are reversed in the two cases. When the seesaw lever 2 is furtherturned counterclockwise, the movable contact 6 is brought intocommunication with the fixed contact 9. Thus, the terminal voltageacross the motor 13 is increased to be substantially equal to the Vc.

As mentioned above, the motor 13 thus can be rotated at a low speed orat a high speed in the reverse direction. When the seesaw lever 2 isreleased after zooming operations, it is restored to its initial centerposition by the restoring force of the spring 5, while the motor 13 isstopped. The direction of zooming and the direction of rotation of themotor 13 may be suitably related to each other. Further, it should beunderstood that the seesaw switch is switched in two stages constitutedby the fixed contacts 8 and 9 or fixed contacts 10 and 11 in eitherdirection as shown. It is possible in other embodiments to provide threeor more stages of switching in either direction.

As has been described, according to the present invention, use is madeof a rocker switch, in which a plurality of successively operableswitches are provided on each side of the center of rotation and whichcan be selectively operated in either direction. By operating the firstone of the switches on either side, zooming of the correspondingmultiple lens group in the corresponding direction and at apredetermined speed can be obtained. Zooming speeds can be changed byoperating the second switch by further turning the seesaw switch. Thus,the zooming speed can be changed without changing the operator's fingerposition. Maneuverability of the operated camera supported by both handsthus can be improved.

Further, the zooming speed can be successively operated from the firstlow speed toward higher speeds, so that it is possible to preventmalfunction. The speed increase can be in one or more stages.

Furthermore, where spring members are used as the movable contacts ofthe seesaw switch as in the above embodiment of the present invention agiven zooming speed can be reliably selected by the operator by sensingthe back pressure that is exerted onto his finger by the spring member,and such an arrangement can be used to make speed changes in stepwisemanner.

While the invention has been described in detail above, it is to beunderstood that this detailed description is by way of example only, andthe protection granted is to be limited only within the spirit of theinvention and the scope of the following claims.

What is claimed:
 1. In combination, a zoom lens comprising a movableportion which controls the focal length of said lens, motor means fordriving said movable lens portion to cause said lens to zoom, manuallyoperable means and circuit means for controlling said motor means tocause said lens to zoom either in the focal distance shortening or thefocal distance lengthening direction and to cause said zooming in eachof said directions to occur at one of at least two predetermined speeds,said manually operable means comprising a rocker member, means topivotally mount said rocker member at about its center portion forrocking motion to either side of a neutral position of said rockermember on said mounting means, spring means normally biasing said rockermember to said neutral position, said control circuit means comprisingat least first and second switch means, said switch means comprising acontact member on each end of said rocker member; and said switch means,said contact member and said control circuit means being so arrangedthat rocking motion manually applied to said rocker member to one sideof said neutral position to cause the corresponding one of said contactmembers to close a first one of said corresponding first and secondswitch means will cause said lens to zoom at a first predetermined speedin one of said directions, and continued motion of said rocker member tosaid one side will close the second one of said switch means to causezooming of said lens in said one of said directions at a secondpredetermined speed; and motion of said rocker to the other side of saidneutral position will cause similar zooming motions of said lens in theother of said directions.
 2. The combination of claim 1, wherein saidsecond predetermined speed is faster than said first predeterminedspeed.
 3. The combination of claim 1 or 2, wherein said control circuitcomprises an array of resistors and transistors between a power supplyand said lens motor means so arranged that a fraction of the full powersupply voltage is applied to said motor to achieve a slower zoom speedwhen one of said first and second switch means is activated and tosupply substantially the full power supply voltage to said motor toachieve a maximum zoom speed when the other of said first and secondswitch means is activated by said rocker member.
 4. A method ofcontrolling the speed and direction of motion of the motor drivenmovable lens portion of a zoom lens comprises the use of a singlemanually operated rocker member, biasing said rocker member to a neutralposition from which it can be moved in two opposite directions,providing two sets of at least first and second switch means each to beoperated by said rocker member when moved in each of said two oppositedirections, and providing control circuit means activated by all of saidswitch means and so arranged between a power supply and the motordriving said movable lens portion that a fraction of the full powersupply voltage is applied to said motor to achieve a slower zoom speedwhen one of said first and second switch means is activated by saidrocker member and to supply substantially full power supply voltage tosaid motor to achieve maximum zoom speed in the same direction when theother of said first and second switch means is activated by said rockermember; and said control circuit means being further so arranged thatmotion of said rocker to the other side of said neutral position willcause similar zooming motions of said lens in the other of saiddirections.